Apparatus for displaying image on liquid crystal pixels arranged in matrix layout

Abstract

A plurality of pixel elements are arranged in a matrix layout, and an alternating current exciting signal having a plurality of exciting pulses is supplied to each pixel element. Each pixel element has a first MOS-FET in which one picture signal is received at a drain every one horizontal scanning period, one scanning signal is received at a gate every one frame period and a charge signal having a charge voltage relating to a picture voltage of the picture signal is output from a source, a second MOS-FET in which the alternating current exciting signal is received at a drain, the charge signal is received at a gate and a pixel electrode voltage of a pixel electrode signal relating to the charge voltage is output from a source, a condenser for maintaining the charge voltage of the charge signal until a next frame period, and a liquid crystal displaying device for emitting light according to the pixel electrode signal to display a pixel image. Because the pixel electrode voltage relates to the picture voltage, a brightness of the pixel image relates to the picture signal, so that an excellent displaying characteristic in gray scale. Also, a frequency of the pixel electrode signal is the same as that of the alternating current exciting signal, so that any flicker in an image composed of the pixel images can be prevented.

What is claimed is: 
     
       1. A liquid crystal displaying apparatus, comprising: a plurality of pixel elements arranged from a first line of a first column to an M-th line of an N-th column (N and M are respectively an integral number) in a matrix layout;   a picture signal electrode actuating circuit for outputting a plurality of N picture signals having picture voltages to N picture signal electrodes in one-to-one correspondence every one horizontal scanning period, each of the picture signal electrodes being connected with one column of M pixel elements;   a scanning signal electrode actuating circuit for outputting a plurality of M scanning signals having a scanning voltage M scanning signal electrodes in one-to-one correspondence every one frame period corresponding to M horizontal scanning periods, each of the scanning signal electrodes being connected with one line of N pixel elements; and   an alternating current exciting signal outputting circuit for outputting an alternating current exciting signal having a plurality of exciting pulses of an exciting voltage and an exciting frequency, each of the pixel elements comprising:     a first switch for receiving one picture signal output from the picture signal electrode actuating circuit through one picture signal electrode and outputting a charge signal set at a charge voltage relating to the picture voltage of the picture signal in cases where one scanning signal output from the scanning signal electrode actuating circuit through one scanning signal electrode is received;   a second switch having a control terminal, a first main terminal and a second main terminal, said first main terminal connected to said alternating current exciting signal outputting circuit for receiving the exciting pulses of the alternating current exciting signal output from the alternating current exciting signal outputting circuit, said control terminal connected for receiving the charge signal from the first switch, said second main terminal connected for outputting a pixel element signal, of which a pixel electrode voltage is determined according to the charge voltage of the charge signal set by the first switch and a frequency is the same as the exciting frequency of the alternating current exciting signal, in cases where the charge signal is received; and   a liquid crystal displaying element for displaying a pixel image in a gray scale according to the pixel element signal output from the second switch on condition that a brightness of the pixel image changes with the pixel electrode voltage of the pixel element signal.   
     
     
       2. A liquid crystal displaying apparatus according to claim 1, further comprising: a charging voltage maintaining circuit for maintaining the charge voltage of the charge signal output from the first field effect transistor until a next scanning signal is received by the first field effect transistor.   
     
     
       3. A liquid crystal displaying apparatus according to claim 1 in which the first switch comprises a first field effect transistor having a gate connected with the scanning signal electrode, a first main terminal connected with the picture signal electrode and the charge signal is output from a second main terminal, and the second switch comprises a second field effect transistor in which said control terminal comprises a gate connected with the second main terminal of the first field effect transistor and said second main terminal is connected with the liquid crystal displaying element. 
     
     
       4. A liquid crystal displaying apparatus according to claim 2 in which the charging voltage maintaining circuit comprises a condenser in which one terminal is connected with the second main terminal of the first field effect transistor and the gate of the second field effect transistor. 
     
     
       5. A liquid crystal displaying apparatus, comprising: a plurality of pixel elements arranged from a first line of a first column to an M-th line of an N-th column (N and M are respectively an integral number) in a matrix layout;   a picture signal electrode actuating circuit for outputting a plurality of N picture signals having picture voltages to N picture signal electrodes in one-to-one correspondence every one horizontal scanning period each of the picture signal electrodes being connected with one column of M pixel elements;   a scanning signal electrode actuating circuit for outputting a plurality of M scanning signals having a scanning voltage M scanning signal electrodes in one-to-one correspondence every one frame period corresponding to M horizontal scanning periods, each of the scanning signal electrodes being connected with one line of N pixel elements; and   an alternating current exciting signal outputting circuit for outputting an alternating current exciting signal having a plurality of exciting pulses of an exciting voltage and an exciting frequency, each of the pixel elements comprising:     a first field effect transistor, having a gate, a first main terminal and a second main terminal, for receiving one picture signal output from the picture signal electrode actuating circuit through the first main terminal, receiving one scanning signal output from the scanning signal electrode actuating circuit through the gate and outputting a charge signal set at a charge voltage relating to the picture voltage of the picture signal through the second main terminal;   a second field effect transistor, having a gate, a first main terminal and a second main terminal, for receiving the exciting pulses of the alternating current exciting signal output from the alternating current exciting signal outputting circuit through the first main terminal, receiving the charge signal from the first field effect transistor through the gate and outputting through the second main terminal a pixel element signal, of which a pixel electrode voltage is determined according to the charge voltage of the charge signal set by the first field effect transistor and a frequency is the same as the exciting frequency of the alternating current exciting signal, the exciting voltage of the alternating current exciting signal being positive and being equal to or greater than a differential voltage obtained by subtracting a threshold voltage of the second field effect transistor from the charge voltage of the charge signal applied to the gate of the second field effect transistor in cases where the second field effect transistor has an N channel, and the exciting voltage of the alternating current exciting signal being negative and being equal to or lower than a differential voltage obtained by adding the threshold voltage of the second field effect transistor and the charge voltage of the charge signal applied to the gate of the second field effect transistor in cases where the second field effect transistor has a P channel, and   a liquid crystal displaying element for displaying a pixel image according to the pixel element signal output from the second field effect transistor on condition that a brightness of the pixel image depends on the pixel electrode voltage of the pixel element signal.   
     
     
       6. A liquid crystal displaying apparatus according to claim 5 in which a dielectric layer having a specific resistance higher than that of a liquid crystal layer of the liquid crystal displaying element is arranged on the liquid crystal displaying element to absorb a direct current voltage component included in the pixel element signal in the dielectric layer. 
     
     
       7. A liquid crystal displaying apparatus according to claim 5, further comprising a phase synchronizing unit for synchronizing the alternating current exciting signal output from the alternating current exciting signal outputting circuit with the scanning signal applied to the gate of the first field effect transistor to fix a phase relationship between the scanning signal and the alternating current exciting signal. 
     
     
       8. A liquid crystal displaying apparatus according to claim 5 in which a metallic layer is arranged on the second main terminal of the second field effect transistor, a pixel electrode is arranged on the liquid crystal displaying element, and an insulating layer is arranged between the metallic layer and the pixel electrode to connect the second field effect transistor and the liquid crystal displaying element in capacitive coupling. 
     
     
       9. A liquid crystal displaying apparatus according to claim 1 in which a common line connects the alternating current exciting signal outputting circuit and the first main terminal of the second field effect transistor, a pixel electrode is arranged on the liquid crystal displaying element to be connected with the second main terminal of the second field effect transistor, and a metallic shielding layer is arranged between the common line and the pixel electrode. 
     
     
       10. A liquid crystal displaying apparatus, comprising: a plurality of pixel elements arranged from a first line of a first column to an M-th line of an N-th column (N and M are respectively an integral number) in a matrix layout;   a picture signal electrode actuating circuit for outputting a plurality of N picture signals having picture voltages to N picture signal electrodes in one-to-one correspondence every one horizontal scanning period, each of the picture signal electrodes being connected with one column of M pixel elements;   a scanning signal electrode actuating circuit for outputting a plurality of M scanning signals having a scanning voltage to M scanning signal electrodes in one-to-one correspondence every one frame period corresponding to M horizontal scanning periods, each of the scanning signal electrodes being connected with one line of N pixel elements;   an alternating current exciting signal outputting circuit for outputting an alternating current exciting signal having a plurality of exciting pulses of an exciting voltage and an exciting frequency;   a pulse supplying circuit for supplying a plurality of reset pulses of a reset pulse signal to each of the pixel elements;   a direct current voltage source for applying a reference voltage to each of the pixel elements; and   a phase synchronizing unit for synchronizing the reset pulse signal output from the pulse supplying circuit with the alternating current exciting signal output from the alternating current exciting signal outputting circuit to output one first reset pulse of the reset pulse signal just before one leading edge of each exciting pulse of the alternating current exciting signal and output one second reset pulse of the reset pulse signal just before one trailing edge of each exciting pulse of the alternating current exciting signal, each of the pixel elements comprising     a first field effect transistor for receiving one picture signal output from the picture signal electrode actuating circuit through one picture signal electrode at a first main terminal and outputting a charge signal set at a charge voltage relating to the picture voltage of the picture signal from a second main terminal in cases where one scanning signal output from the scanning signal electrode actuating circuit through one scanning signal electrode is received at a gate;   a second field effect transistor for receiving the charge signal output from the first field effect transistor at a gate, receiving the alternating current exciting signal output from the alternating current exciting signal outputting circuit at a first main terminal and outputting a source pulse signal of which a source pulse voltage is determined according to the charge voltage of the charge signal and a frequency is the same as the exciting frequency of the alternating current exciting signal;   a condenser, of which one terminal is connected with the second main terminal of the second field effect transistor and the other terminal is connected with a connecting line, for removing a direct current voltage component from the source pulse signal output from the second field effect transistor;   a third field effect transistor for receiving the reset pulses of the reset pulse signal output from the pulse supplying circuit at a gate, receiving the reference voltage applied from the direct current voltage source at a second main terminal and outputting an alternating current pulse signal from a first main terminal to the connecting line on condition that a pixel electrode voltage of the alternating current pulse signal is reset to the reference voltage in synchronization with each of the reset pulses, the pixel electrode voltage reset to the reference voltage in synchronization with each first reset pulse is increased to a highest value relating to the source pulse voltage of the source pulse signal applied to the condenser and the pixel electrode voltage reset to the reference voltage in synchronization with each second reset pulse is decreased to a lowest value relating to the source pulse voltage of the source pulse signal applied to the condenser; and     a liquid crystal displaying element for displaying a pixel image according to the alternating current pulse signal output from the third field effect transistor through the connecting line on condition that a brightness of the pixel image depends on the pixel electrode voltage of the alternating current pulse signal.   
     
     
       11. A liquid crystal displaying apparatus according to claim 10 in which the exciting voltage of the alternating current exciting signal is positive and is equal to or higher than a differential voltage obtained by subtracting a threshold voltage of the second field effect transistor from the charge voltage of the charge signal applied to the gate of the second field effect transistor in cases where the second field effect transistor has an N channel, and the exciting voltage of the alternating current exciting signal is negative and is equal to or lower than a differential voltage obtained by adding the threshold voltage of the second field effect transistor and the charge voltage of the charge signal applied to the gate of the second field effect transistor in cases where the second field effect transistor has a P channel. 
     
     
       12. A liquid crystal displaying apparatus according to claim 10 in which a capacity of the condenser is equal to or higher than a capacity of the liquid crystal displaying element.